The prior art, as shown in U.S. Pat. No. 3,586,824, issued June 22, 1971, to Edward A. Barney, includes a heating appliance in which a plate is adapted to support a cooking utensil and is moved downwardly toward a heating element by weight of the utensil. Switching means are provided whereby the heating element is energized upon downward movement of the plate and deenergized upon upward movement of the plate. The Barney construction has some disadvantages in that the plate is interposed between the cooking utensil and the heating element and therefore prevents direct conduction of heat from the element to the utensil.
Further, most of the surface units now produced are of the plug-in type, wherein the terminals of the heating element have plug-in connection with terminals within a terminal block, so that the heating element and customary drip pan may be easily removed from operative position on the stove top for cleaning purposes. Prior art, such as U.S. Pat. No. 3,042,783, issued July 3, 1962, to C. S. Mertler, shows a plug-in surface unit, but flow of electrical current to the heating element is under control of a thermal sensing unit and in such art the current flow to the heating element is not automatically interrupted when a cooking utensil is removed therefrom.
It is a known fact that considerable electrical energy is wasted by reason of the fact that the housewife does not immediately turn the control switch to "off" position after she removes a cooking utensil from the heating element, or forgets to turn the switch "off" until some time later. My invention provides the benefit of plug-in surface units and embodies means to immediately interrupt flow of electrical current to the heating element when the utensil is removed therefrom.